French press is the most forgiving brewer there is, which is also why most people never get a great cup out of it. Two numbers fix that: the ratio and the steep time.
The ratio
Start at 1:15 by weight. For a standard 1 litre press that is 65 g of coarse coffee and 975 g of water. Go to 1:12 for a heavier, syrupy cup, or 1:17 if the coffee tastes muddy.
Because French press uses a metal mesh and not paper, some fine particles reach the cup. That adds body, but it also makes over-extraction taste harsh. Coarse grind plus a shorter steep is the standard defence.
By press size
Presses are sold by volume, and the numbers do not line up with cups. Here are the actual weights.
| Press size | Water | Coffee at 1:15 |
|---|---|---|
| 3 cup / 350 ml | 340 g | 23 g |
| 4 cup / 500 ml | 480 g | 32 g |
| 8 cup / 1 L | 970 g | 65 g |
| 12 cup / 1.5 L | 1450 g | 97 g |
The steep
Four minutes is traditional and works, but it is not the only good answer. Grind and time trade off against each other.
Coarse grind plus 4 minutes and medium-coarse grind plus 3 minutes both produce good cups. The mistake is fine grind plus 4 minutes, which pulls out harsh compounds and gives a bitter, drying cup.
The two-stage method that beats the classic recipe
Break the crust at 4 minutes and let the grounds settle for another 4 before pressing. During those second four minutes most suspended fines fall to the bottom, and the cup you pour is noticeably cleaner.
Do not press all the way down. Press just until you meet resistance from the bed, then pour. Pressing to the bottom agitates fines and muddies the cup.
Common mistakes
These account for most bad French press coffee:
- Grinding too fine. It should look like raw sugar, not sand.
- Not weighing. A heaped spoon is a 100 percent error.
- Steeping too long with a fine grind. Compounds that taste good at 3 minutes taste harsh at 8.
- Pressing hard. Squeezing the bed pushes fines through the mesh.
- Leaving coffee on the grounds. Decant the rest into a second vessel or it keeps extracting and turns bitter.